When numerically controlled machines, particularly machine tools or robots, are subjected to dangerous situations, an emergency braking of the axle drives is provided which is either released by an EMERGENCY-STOP operator control, by external devices, or as the result of an internal error reaction. When such an emergency tripping takes place, the drives of the numerically controlled machine are supposed to be linearly decelerated in the shortest possible time through the appropriate selection of speed setpoints. About 30 to 50 milliseconds after the emergency tripping, a short-circuit braking which is necessary from a standpoint of safety engineering is then introduced so that, in any case, the motors come to a standstill while the control system is by-passed.
When such an emergency braking takes place, the numerically controlled machine can no longer adhere to the given tool path, since the axles are braked independently of one another. Even when the axle drives are synchronized to allow the axles to be adapted with respect to time to the axle exhibiting the lowest deceleration, path deviations occur, at least in the case of curved paths.
The least significant problem encountered in such an emergency braking operation is posed by the difficulties entailed in resuming the machining process. Far greater problems are encountered when a path deviation causes the tool to collide with the workpiece or with other objects or when, for example, several robots working side-by-side collide with one another.